Liquid crystal display elements are being used in watches, calculators, various measurement instruments, automobile panels, word processors, electronic organizers, printers, computers, televisions, clocks, advertising boards, etc. Typical examples of the liquid crystal display mode include TN (twisted nematic) mode, STN (super twisted nematic mode) mode, and vertical alignment mode or an IPS (in-plane-switching) mode that uses TFTs (thin film transistors). Liquid crystal compositions used in these liquid crystal display elements are required to be stable against external stimuli such as moisture, air, heat, and light, stay in a liquid crystal phase in a temperature range as wide as possible around room temperature, exhibit low viscosity, and operate at a low drive voltage. A liquid crystal composition is constituted by several to dozens of compounds in order to optimize dielectric anisotropy (Δ∈) and/or refractive index anisotropy (Δn), etc., for individual display elements.
In a vertical alignment (VA) display, a liquid crystal composition having a negative Δ∈ is used and, in an horizontal alignment display such as TN mode, STN mode, or IPS (in-plane-switching) mode, a liquid crystal composition having a positive Δ∈ is used. There has been a report of a driving mode with which a liquid crystal composition having a positive Δ∈ is made to align vertically in the absence of applied voltage and a horizontal electric field is applied to perform display. There is an increasing need for a liquid crystal composition with a positive Δ∈. Meanwhile, low voltage driving, high speed response, and a wide operation temperature range are highly desirable in all driving modes. In other words, a positive Δ∈ with a large absolute value, low viscosity (η), and a high nematic phase-isotropic liquid phase transition temperature (Tni) are desirable. Due to setting of Δn×d, which is the product of Δn and a cell gap (d), the Δn of the liquid crystal composition needs to be adjusted to be within an appropriate range in accordance with the cell gap. Since high-speed response is important in order to use a liquid crystal display element in a television or the like, a liquid crystal composition having a low rotational viscosity (γ1) is desirable.
Examples of the configurations of a liquid crystal composition directed to high-speed response include a liquid crystal composition that contains a combination of a compound represented by formula (A-1) or formula (A-2) below which is a liquid crystal compounds having a positive Δ∈ and a compound represented by formula (B) below which is a liquid crystal compound having a neutral Δ∈. The features of such liquid crystal compositions are that the liquid crystal compound having a positive Δ∈ has a —CF2O— structure and that the liquid crystal compound having a neutral Δ∈ has an alkenyl group. These features are widely known in the field of liquid crystal compositions (refer to PTL 1 to PTL 4).

Meanwhile, with the expansion of applications of liquid crystal display elements, the operation method and the production method for liquid crystal display elements have undergone significant changes. In order to follow up these changes, optimization of properties other than the basic physical properties that have been known in related art is required. That is, liquid crystal display elements that use liquid crystal compositions and have come to be widely used are of a VA mode, IPS mode, or the like, and display elements with super large screen size of 50 or larger have been put to practice and are now being widely used. As the substrate size increases, a one drop fill (ODF) method has become the mainstream method for injecting a liquid crystal composition into a substrate, thereby replacing a conventional vacuum injection method. However, degradation of display quality caused by drop marks that occur when the liquid crystal composition is dropped onto a substrate has become a problem. In a liquid crystal display element production process based on the ODF method, optimum amounts of liquid crystals need be injected by dropping according to the size of a liquid crystal display element. If the injection amount significantly deviates from the optimum value, the balance among the pre-designed refractive index and drive electric field of the liquid crystal display element will be adversely affected and display failures such as nonuniformity and poor contrast will result. In particular, for a small-size liquid crystal display element frequently used in smart phones that have become prevalent in recent years, it is difficult to control the deviation from the optimum value within a particular range since the optimum amount of the liquid crystals to be injected is small. Accordingly, in order to produce liquid crystal display elements while maintaining high yield, for example, a liquid crystal composition needs to be less affected by impacts and rapid changes in pressure inside a dropping machine during injection of liquid crystals by dropping and allow stable continuous dropping over an extended period of time.
As such, a liquid crystal composition used in an active matrix driving liquid crystal display element driven by TFTs and the like is required to maintain properties and performance, such as high-speed response, desirable for a liquid crystal display element, to exhibit high resistivity and high voltage holding ratio and be stable against external stimuli such as light and heat as have been emphasized in the past, and to be developed by taking into account the liquid crystal display element production method.